This document summarizes several intestinal and urogenital flagellates including Giardia lamblia, Trichomonas vaginalis, Dientamoeba fragilis, Trichomonas tenax, Chilomastix mesnili, Retortamonas intestinalis, and Trichomonas hominis. It describes the morphology, life cycles, transmission routes, clinical manifestations, diagnosis, treatment and prevention of these parasites. Giardia lamblia is a common cause of parasitic diarrhea and is transmitted through ingestion of cysts from contaminated food, water or surfaces. Trichomonas vaginalis causes the sexually transmitted infection trichomoniasis through sexual contact.

1. MT 20: PARASITOLOGY
INTESTINAL AND UROGENITAL FLAGELLATES
PHYLUM: SARCOMASTIGOPHORA
SUBPHYLUM: MASTIGOPHORA
CLASS: ZOOMASTIGOPHORA
ORDER: TRICHOMONADIDA (Trichomonas spp.)
ORDER: RETORTAMONADIDA (Chilomastix spp.)
ORDER: DIPLOMONADIDA (Giardia lamblia)
DIFFERENT STAGES OF DEVELOPMENT:
1. Trophozoite stage – feeding stage, motile stage,
replicating stage
2. Cystic Stage – resting stage; highly resistant to
destruction and can survive outside of the host
for several days
Giardia lamblia
• Other names: Giardia intestinalis, Giardia
duodenalis, Lamblia duodenalis, or Lamblia
intestinalis
• Discovered in 1871 by Van Leeuwenhoek in his
own stool
• Disease: Giardiasis, Lambliasis, Traveler’s
diarrhea, “Beaver fever”, Backpacker’s diarrhea,
“Gay Bowel Syndrome
• Most commonly diagnosed intestinal parasite in
the US
• children and adult campers who engage in
recreational water activities are commonly
infected (lakes, rivers, swimming pools, and
water parks)
• A prevalent intestinal parasite and frequently
causes parasitic diarrhea
HABITAT
• duodenum, jejunum, upper ileum
INFECTIVE STAGE: mature cyst/quadrinucleated cyst
MODE OF TRANSMISSION
• ingestion of mature cyst from contaminated
food, water, or hand
• oro-anal intercourse
PERSONS AT RISK OF EXPOSURE:
• Children in day care centers
• MSM (males having sex with males)
• Backpackers and campers
• Travelers to endemic areas
• Persons drinking water from shallow wells
Trophozoite Stage
• bilaterally symmetrical pear-shaped flagellate
• Length: 9-12 um
• Width: 5 – 15 um
• Has a pair of ovoidal nuclei with centrally
located karyosome
• Diagnostic feature: ventral sucking/adhesive
disc which functions as a point of attachment to
the small intestine
• Median bodies: unknown function
• Axoneme: Median line
• Flagella: 4 pairs( anterior, lateral, ventral,
posterior)
• Falling-leaf motility
Cyst Stage
• Cysts are ovoidal and double-walled (diagnostic)
• “football-shaped”
• Length: 9-12 um
• Width: 7-12 um
• Has finely granular cytoplasm
• Axonemes present
• Young cyst: 2 spherical nuclei
• Mature cyst: 4 spherical nuclei
• Median bodies represent retracted flagella
LIFE CYCLE
Acquiring Giardiasis is possible by ingesting
quadrinucleated cysts from contaminated hands, food,
or water. Cysts pass through the stomach and excysts in
the duodenum developing into trophozoites which
actively multiply and attach to the intestinal villi via the
ventral sucking disc. Flattening of the microvilli of the
intestinal wall leads to mechanical irritation of the
microvilli leading to deficiency of digestive enzymes
causing malabsorption or steatorrhea. The trophozoites
may then be found in the jejunum. As the feces enters
the colon and dehydrates, the parasite encysts. Mature
cysts are passed out in the feces and are ingested by a
suscpetible host. Trophozoites are passed out also in
watery stools.
PATHOGENESIS AND CLINICAL MANIFESTATION
Mild to Moderate Infection
• Incubation period: 1-4 wks (average 9 days)
• 50% of infected individuals are asymptomatic
and has spontaneous recovery in mild to
moderate cases in about 6 wks
• Mild Giardiasis: diarrhea
• Symptoms: cramping, diarrheic stools with
excessive flatus (rotten egg odor or hydrogen
sulfide odor), abdominal bloating, nausea,
anorexia

2. Severe to Chronic Infection
• Severe cases causes malabsorption and
steatorrhea
• Flattening of the tips of the microvilli and
shallow crypts
• With inflammation of the mucosa and
hyperplasia of lymphoid follicles
• Ventral sucking disc causes flattening of the
microvilli leading to deficiency of digestive
enzymes causing steatorrhea and
malabsorption
• Passage of greasy, frothy stools that float on
toilet water
• Weight loss, generalized weakness, chills, and
low grade fever
LABORATORY DIAGNOSIS
• Demonstration of trophozoite and cyst in stools
specimens via direct fecal smear
– 3 Stool exams on alternate days to
increase sensitivity
• Duodenal aspirate or biopsy – if parasite is not
found in the feces; demonstrates trophozoites
• Entero-test/Entero-string test: demonstrates
Giardia lamblia trophozoites
– Higher sensitivity; accurate, and
inexpensive
– Specimen: duodenal fluid
– Makes use of a gelatin capsule
Serologic Tests:
• Direct Fluorescent Antibody
• ELISA – to detect Giardia-specific antigen
– High sensitivity
TREATMENT
• Metronidazole
• Tinidazole
• Furazolidone
EPIDEMIOLOGY
• Associated with poor environmental sanitation
• Giardia is found worldwide and infects domestic
and wild animals (e.g., cats, dogs, cattle, deer,
and beavers)
• Waterborne outbreaks are associated with
ingestion of both drinking and recreational
water
• Foodborne outbreaks have also been reported
RISK FACTORS
• Poor hygiene and sanitation
• Overcrowding (mental institutions, day care
centers)
• Immunodeficiency
• Bacterial and fungal overgrowth in the small
intestine
• Homosexual practices
PREVENTION AND CONTROL
• Proper and sanitary disposal of human excreta
• Stop using night soil as fertilizer – resp. for
contaminated food
Dientamoeba fragilis
D. fragilis is believed to be transmitted between human
hosts inside helminth eggs or larvae, particularly those
of Enterobius vermicularis and Ascaris lumbricoides.
DNA of D. fragilis is found in these helminth ova. It
frequently infects children. The complete life cycle of
this parasite has not yet been determined, but
assumptions were made based on clinical data. To date,
the cyst stage has not been identified in D. fragilis life
cycle, and the trophozoite is the only stage found in
stools of infected individuals. D. fragilis is probably
transmitted by fecal-oral route and transmission via
helminth eggs (e.g., Ascaris, Enterobius spp.) has been
postulated. Trophozoites of D. fragilis have
characteristically one or two nuclei, and it is found in
children complaining of intestinal (e.g., intermittent
diarrhea, abdominal pain) and other symptoms (e.g.,
nausea, anorexia, fatigue, malaise, poor weight gain).
CLINICAL MANIFESTATIONS
 diarrhea, abdominal pain, anorexia, nausea,
vomiting, fatigue, and weight loss.
LABORATORY DIAGNOSIS
 Detection of trophozoites in permanently
stained fecal smears (e.g., trichrome)
 This parasite is not detectable by stool
concentration methods.
TREATMENT
 Iodoquinol – DOC
 Paromomycin
 Tetracycline (contraindicated in children under
age 8, pregnant and lactating women)
 Metronidazole
_______________________________________
Trichomonas vaginalis
• Disease: Trichomoniasis (STD)
• Common Name: Trich
• The only pathogenic specie in the genus
• Discovered by Donne in 1836 in purulent
secretion of male urogenital discharge and
female vaginal discharge
• Exists only in the trophozoite stage

3. Trophozoite
• Pyriform shape; tear-drop shape**
• Length: 7-23 um
• 4 anterior flagella
• 5th
flagellum is embedded in the undulating
membrane or axostyle; has barbwire-like
appearance and is responsible for attachment
and tearing up of the vaginal wall which causes
inflammation and intensifying the infection
• Undulating membrane** extends halfway
through the body of the parasite; this structure
is resp. for sweeping nutrients into the
cytostome
• Has a single nucleus that’s anteriorly located
• Has an axostyle that extends throughout the
length of the body and projects posteriorly
• Has chromatin/siderophil granules in the
cytoplasm but more prominent in the costa and
axostyle
• Lacks mitochondria but is replaced by
hydrogenosome which produces ATP
HABITAT
• Males: urogenital tract (urethra, pelvis,
prostate, epididymis)
• Females: vagina ascending to the renal pelvis
REPRODUCTION
• Longitudinal Binary fission
MODE OF TRANSMISSION
• Sexual intercourse
LIFE CYCLE
• The trophozoites live in the urinary or
reproductive tracts until they are passed onto
their next human host via unprotected sexual
contact, where the whole process starts over
again.
PATHOGENESIS AND CLINICAL MANIFESTATION
FEMALES
• Inflammation of the vaginal mucosa
• T. vaginalis are not free living organisms
• Requires human host
• Women will show symptoms of being infected
between five and 28 days after exposure.
• Irritation, inflammation, burning, itching, and a
smelly, frothy, discharge, ranging from green to
yellow to gray are indications of a T. vaginalis
infection.
• Sores will sometimes be present as well, from
the T. vaginalis' barbwire-like flagella.
• Vulvitis and dysuria
• Increased incidence of Trichomoniasis in
postpartum endometritis
• Strawberry cervix
MALES
• Asymptomatic and latent infection
• Responsible for persistent/recurring urethritis
• Most common complication: Prostatitis
• Itching and discomfort inside the penile urethra
esp. during urination
LABORATORY DIAGNOSIS
MALES
• Demonstration of trophozoite in urine, urethral
discharge, prostatic secretions in wet mounts
FEMALES
• Demonstration of trophozoites in urine, vaginal
secretions, cervical secretions, cervical swabs in
wet mounts
MOTILITY PATTERN: Wobbling or rotary, jerky motility
STAINS USED IN MX:
Giemsa
Papanicolau
Romanowsky
Acridine orange
CULTURE:
Diamond’s Modified Medium
Feinberg-Whittington Culture Medium
Bushley’s CM
Roiron’s and Johnson-Trussel CM
CPLM ( Cysteine Peptone Liver Maltose) Medium
TREATMENT
• Both partners must be treated simultaneously
and abstain until treatment is finished,
otherwise they will be continuously re-infecting
each other causing the “Ping-pong effect”
• Metronidazole
• Tinidazole
• Nimorazole
• Ordinazole
EPIDEMIOLOGY
• Worldwide in distribution
• Most commonly acquired STD
• Prevalence is higher in women of child-bearing
age
• Higher prevalence with greater frequency of
sexual intercourse with multiple sexual partners
PREVENTION AND CONTROL
• Sexual abstinence
• Safe sex
• Monogamy
______________________________________________
Trichomonas hominis
• Pentatrichomonas hominis
• Tetratrichomonas hominis
• Trrichomonas intestinalis
• Non-pathogenic; commensal only
• Trophozoite stage only
• Passed out in diarrheic stools
MODE OF TRANSMISSION
• Ingestion of trophozoite from contaminated
food and drinks
– Presence of this parasite in food and
water indicates fecal contamination
HABITAT
 Cecum (large intestine)
DIAGNOSIS
• Demonstration of trophozoite in stools
• Motility pattern: rapid jerky motility

4. TROPHOZOITE
 Pyriform shape
 Length: 5-14 um
 5 anterior flagella plus a posterior flagellum
projecting from the undulating membrane
 Cytostome situated anteriorly opposite to the
 Single nuclei situated anteriorly
 Axostyle extends from the anterior to posterior
along the midaxis
 Undulating membrane** extends all the way
through the entire body of the parasite and is
free trailing at the posterior end
LIFE CYCLE
• Ingestion of trophozoite from contaminated
food and watertrophozoite in the
stomachSIcecum (large intestine)
trophozoite replicatespassed out in stool
ingested by host
EPIDEMIOLOGY
• Prevalence in the Philippines is <1%
______________________________________________
Trichomonas tenax
• Trophozoite stage only
• Non-pathogenic; harmless commensal of the
oral cavity
• Multiplies by longitudinal binary fission
• Can survive for several hours in drinking water
HABITAT
• Oral cavity
MODE OF TRANSMISSION
• Kissing
• Use of common eating and drinking utensils
• Droplet spray from the mouth
PREVENTION: good oral hygiene
DIAGNOSIS: swabbing the tartar between the teeth,
gingival margin, or the tonsillar cryptswet mount or
stained slides
TROPHOZOITE
• Pyriform in shape
• Length: 5-12 um (smaller and more slender than
T. vaginalis)
• 4 flagella plus a 5th
one in the margin of the
udulating membrane which doesn’t reach the
posterior end of the body
• Single nuclei and cytostome
• Undulating membrane** extends ½ to 2/3 of
the body of the parasite
______________________________________________
Chilomastix mesnili
• Non-pathogenic; harmless commensal
• Indicator of fecal contamination of food and
water
• Prevalence in the Phils. Is <1%
• Treatment is not necessary
HABITAT
• Cecum (large intestine)
MODE OF TRANSMISSION
• Ingestion of cysts from contaminated food and
water
DIAGNOSIS:
• Demonstration of trophozoites and cysts in
stools
PREVENTION
• Proper sanitation and personal hygiene
TROPHOZOITE
• Length: 6-10 um
• Assymetrical pear-shaped due to the **spiral
groove running obliquely across the ventral
surface
• Single spherical nucleus with a centrally located
karyosome and achromatic fibrils
• 3-4 anterior flagella arising from the
blepharoplasts and a more delicate one within
the prominent cytostome
• Cleft-shaped cytostome extends ½ of its body
length
• Motility pattern: boring progressive motility
with slow rotation of the body
CYST
• Lemon-shaped with nipple-like** or knob-like
protuberance
• Length: 6-10 um
• Single nucleus with centrally located karyosome

5. • Cytostome extends throughout the body of the
parasite
• Cytostomal fibril has a **“Shepherd’s crook”
appearance
LIFE CYCLE
• Ingestion of cyst from contaminated food and
watercyst in the stomachSIcecum (large
intestine)excystation trophozoite replicates
undergoes encystation trophozoite and
cyst passed out in stool cyst ingested by host
______________________________________________
Retortamonas intestinalis
• Retortamonas intestinalis is a small flagellate
and is rarely encountered.
• found in both warm and temperate climates
• non-pathogenic; harmless commensal
• Indication of fecal contamination
MODE OF TRANSMISSION
• Ingestion of cyst from contaminated food and
water
HABITAT
• Cecum
LABORATORY DIAGNOSIS
• Demonstration of cyst and trophozoite from
stools
TROPHOZOITE
• The trophozoite is small
• Large single nucleus at the anterior portion with
small compact karyosome
• Length: 4 – 9 um.
• Motility: jerky and rotational
• 2 anterior flagella and a prominent cytosome
that can be seen in an unstained preparation
CYST
• The cysts are small and pear shaped.
• Length: 4-7 um with
• 1 large nucleus frequently near the centre.
• The fibril arrangement: “birds beak”.
LIFE CYCLE
• Ingestion of cyst from contaminated food and
watercyst in the stomachSIcecum (large
intestine)excystation trophozoite replicates
undergoes encystation passed out in
stool cyst ingested by host

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